Blueprint machine



u E. L. DAVENPORT 2,351,251

BLUE PRINT MACHINE Filed Feb. 6, 1942 4- Sheets-Sheet 1 2 "m .7 n2 25 -42 L 38 d 20 73 ES 40 562 E ii INVENTOR.

June 13, 1944. E. L. DAVENPORT 2,351,251

BLUE PRINT MACHINE Filed Feb. 6, 1942 4 Sheets-Sheet 2 FIG. 4.

N 35 as I r I I I I I I I I I I I I 50 M2 I 48 .INYENTOR.

I June 13, 1944.

ill!

E. L. DAVENPORT 2,351,251

BLUE PRINT M ACHINE Filed Feb. 6, 1942 4 SheeB-Sheet 5 June 13, 1944.

E. L DAVENPORT BLUE PRINT MACHINE Filed Feb. 6, 1942 4 Sheets-Sheet 4 Patented June 13, 1944 UNITED STATES PATENT OFFICE 2,351,251 BLUEPRINT MACHINE Emerson L. Davenport, Grand Rapids, Mich. Application February 6, 1942, Serial No. 429,735

' 1 Claim. .('c1. 240-2) My invention relates generally to means for controlling the intensity of light reaching determinable portions of a flat or curved surface from the filament of an electric lamp positioned stationary there, and more particularly to obtaining equal light intensity and distribution upon the working or operating surface of a copying machine using photo-sensitive copying papers or fabrics.

One of the main objects of my invention is to produce blue-prints which have lines of uniform Weight and which will be readable at all points thereon, and it will be understood that this result is obtained by creating a machine in which the amount or intensity of light reaching any unit of area of the working or operating surface equals the amount or intensity of light reaching any other unit of area thereof. The term blueprint is intended to include not only the blueprint process but also the Van Dyke, the various direct line, and so-called photo-copyprocesses, all of which require to have light spread uniformly over the surface to which they, in combination with a drawing or manuscript to be copied, are applied.

I am aware that this object is accomplished in many ways in machines already devised. Improvements claimed will comprise a satisfactory accomplishment of this object coupled with sim-v plicity of structure in the machine, whereby it is economical to construct, and whereby it can be built of parts relatively light in weight resulting in the machine being readily portable.

Also, by reason of my new. means of controlling and distributing available light to requiring areas in determinable proportions I am able to use the relatively inexpensive and readily available bulb type of incandescent filament lamp rather than the more costly and often less readily available tube type lamp or the more complicated and more troublesome arc-lamp, both of which usually require for their operation a transformer, which may be both costly and heavy, rendering a machine in which it is incorporated less readily portable.

Also, my machine is easy to operate, the automatically retractable curtain brake aiding in the easy and expedient operation. v

Another advantage resulting from my improved means of utilizing a very large percentage of the light generated in the lamps is that the machine is both efficient and economical in relation to the amount of current consumed in its operation.

Also, because of my new idea of utilizing a glass cylinder as the structural foundation of a copy-' ing machine, much additional structure and weight can be dispensed with, and it is possible to incorporate a modern and agreeable appearance in the construction of a copying device at relatively small cost.

Another feature of advantage is my use of a retaining curtain as nearly white as may be upon its side facing the inside of the cylinder, whereby light is reflected therefrom on the occasion of utilizing only a portion of the working surface of the cylinder, as in making a small copy. This curtain being a dark color upon its reverse side whereby light is prevented from passing through and troubling the vision of the operator or other occupants of the room in which the machine is used.

Other objects of this invention will appear in the following description and drawings, which illustrate a preferred embodiment of this invention, it being understood that this preferred embodiment is intended generally to explain and not to limit in any manner other applications of said invention.

In the drawings:

Fig. 1 is a side view of a blueprint machine constructed so as to utilize the principles of my invention.

Fig. 2 is an end View of the left hand end of Fig. 1.

Fig. 3 is an end View of the right hand end of Fig. 1.

Fig. 4 is a fragmentary sectional view of the upper right hand corner of Fig. 1.

Fig. 5 is a schematic view illustrating the dis tribution of light along the length of my ma chine.

Fig. 6 is a graph depicting the various light intensities along the cylinder of the machine.

Fig. 7 is a cross sectional view disclosing one type of my reflector.

Fig. 8 is a diagrammatic view illustrating one method of constructing the desired type of re flector.

Fig. 9 is a plan view of my light reflector prior to its installation around the bulb.

Fig. 10 is a sectional view taken along the plane of the line lfl-l 0 of Fig. 9.

' Fig. 11 is an underplan view of an electric light bulb equipped with my inventive idea.

Fig. 12 is a diagrammatic view'looking at the end of the light source or bulb.

Like numerals refer to like parts throughout the several views.

As is shown in Figs. 1 and 4, numeral l0 indicates a transparent cylinder, as of glass, and its ends are received in circular grooves in the channel members which, in turn, are located within and may be fastened to the ring members II and I2. The channel members are identical at each end of the glass cylinder and thus the showing of Fig. 4 is sufficient to explain the full construction. Suitable packing l3 properly seats the end of the cylinder within its groove.

Also, ring members ll and I2 are identical except that one is right hand and one is left hand. Thus the description of one will suffice.

As shown in Fig. 4, the ring member H has the L-shaped portion forreceiving the channel member, just described, then extends inwardly to form the circumferential portion 14, then is curved as shown at l5 to form an annular groove, then extends axially at It and terminates in the bead portion IT.

The end plate is centrally bulged as at 2|, then extends radially outwardly at 22, this portion 22 having ventilating holes 23 formed therein as shown, then is bent at right angles to form the flange 24. The flange 24 snaps onto the bead portion I! and thus means is provided for quickly and easily attaching the end plate 20 and its appurtenances into place.

The other end plate 25 also has a radially extending portion 25,, withholes- 21, and terminates 31, right and left hand, receive the stems 32 of the winding spring 33 of the roller 34 which carries the curtain 35. This curtain is adapted to be drawn around the glass cylinder and its mechanism, as just referred to, provides for its extension andwithdrawal in the manner of the usual window shade.

Ears or stops H2 are provided to rise from the ring members H and I2, see Fig. 1, these ears or stops serving as hooks upon which to position thetwo ends of a rod attachedto the free end of. the curtain. Thus positioned upon its stops, the spring tensioned roller, holding the other end, tends to maintain a tightness in the curtain and thus holds it in contact with the cylinder, thereby providing satisfactory contact between the copying paper and the original drawing, this contact being desirable to insure sharp and exact reproduction of lines;

This curtain is as nearly white as may be upon its side facing the light source, for the purpose of providing over the entire surface of the cylinder a white reflecting medium at times when this surface is not coveredby a white paper drawing, as when only a portion of said surface is so covered by a drawing smaller than the maximum size which the machine is designed to accommodate. 7

Support 39 extends downwardly through the portion l4 of the ring member H, is return bent at 36, then is curved around and against the portion l5 and welded thereto at 3.1.

The return bent portions of the support have an opening therethrough to receive the pipe 38 which is threaded to receive the nut 39; As shown in Fig. 4 the electrical conductor 49,511.11;- ably insulated against heat, passes through this pipe and thus both lights are placed in the same circuit.

The support 38 also has an opening 4| therethrough so that the pin '42 may operate therethrough as will now be described. The support 3|, except for this last mentioned opening, is substantially identical with the support 30.

As is shown in Figs. 2 and 3, respectively, pipes 43' and 44 are bent to the shape shown and, see Fig. 4, near the top of the bight of the pipe 44 an opening 45 is formed for the sliding plunger 46, and a smaller hole for the pin 42, this pin 42 bein threaded at 48 into the plunger 46. The pin 42 is enlarged at 49 to form a shoulder which prevents the spring 55 from too great retractive movement. The enlarged portion 49 is grooved at 5| to receive the pin 52 which is rigid with the roller 34.

It will thus be understood that assembly of the several parts is easily accomplished and then, upon the user of the machine pushing in the plunger 45 that the groove 5| in the pin receives the pin 52 and thus the curtain is held against retractive movement. This is desirable when the curtain has been extended and thus is ready for the laying of the tracings or the like thereupon with. the sensitized paper therebehind, whereupon the operator may simply pull the curtain slightly thus causing the pin 52 to lift out of its groove whereupon the small spring 50 acts to withdraw the plunger and its pin 49 out of the path of the bodily revolving pin 52 and thus the curtain will automatically be retracted by means of its curtain spring 33.

The pipes 43 and 44, see Figs. 2 and 3, previously referred to, are bent as shown to form legs and feet for the machine.

The end structure 43 has a cross brace 53 extending underneath and riding in the groove [5 of the ring member l2 and similarly the structure 44 hasa cross brace 54' Diagonal, braces 55 and 55 extend as shown. See Figs. 1 and 2. Fig. 3 merely shows the holes for these diagonals. These diagonal braces 55 and 56 serve the double purpose of providing tension means for position ing the supporting structures against the ends of the cylinder, and where they cross of providing a handle convenient for carrying the machine from place to place, inan invertedpo'si tion, in the manner in which a suitcase is carried, with onehand. The pipe 38, besides serving its previously mentioned function, similarly serves as the diagonals, namely, as a tension member.

As is shown in Fig. 4, a nut 51 is welded at 58' onto the inside of the'end plate 20 and the other end plate 25 is similarly equipped. The nut 51 receives the threaded nipple 59, slotted at 60 for entry of the electrical conductonand the light socket 6! is suitably supported upon the nipple as. shown. The light bulb 62 is carried by this socket. At the other end of the cylinder, see Fig. 1, a similar bulb63 is provided. These bulbs may be of any desired size, for instance, a No. 4 Photoflood might be used. Or, a 750 Mazda light bulb has been found to sufiice in a machine of my dimensions, namely", 12" diameter and 24" long. The numeral indicates an automatic timer, see Figs. 1 and 3. The electrical conductors are not shown in full but it is to be understood that the two lights, 62 and 63,, are controlled by the timer as will be readily understoodby those skilled in this art.

The collar 64, see Fig. 4, snugly slides upon the socket BI, and its enlarged portion65, grooved at 65, provides for the reception of the reflector 68. Slots 61 permit inward springing of the por-.

tions 65 whereby the reflector may be entered into the groove 65..

The reflector 68 is mirrored or silvered upon its rear face as indicated at 69.

Referring to Fig. 5, 62 and 63 are the sources of light. The line B-B is the surface of the cylinder and also this line serves as a base line for the graph lines A and C. The height of these curves above the base line indicates the light intensity at that point. For example, directly underneath the light 63, the distance D graphically represents the light at that point from this light 63 only. At point F the vertical distance represents the light therefrom either light 62 or 63 as this point is equidistant from both sources. I

To obtain the total light at any point, as undemeath the light 63, distance D must be added to distance G and this combined effect is shown in Fig. 6.

Still referring to Fig. 5, however, H indicates one end of the cylinder and J the other end. The dimensions shown are merely illustrative.

In Fig. 6 the base lin is K-K. The addition of the two curves results in the new curve AC. At its central portion, as shown, its height is 2F. A line L-L is horizontally drawn through this point and the small areas over this line, at either side thereof, represent light which is unnecessary to maintain equal intensity at these points as compared to the light intensity 2F as a standard. So, by calculating the various vertical distances, as typified by dimension M, with respect to the ordinate D, this latter representin the light emitted from 63 at that point along the length of the cylinder, the percentage of reduction is found. And, this gives the percentage of coverage at the corresponding point on the light bulb. In other words, directly below the light source 63, the relation of M to D would be as the relation of ID to ll. See Fig. 9. This calculation is continued and thus the shape of the vanes I2 is arrived at.

, More specifically. as shown in Fig. 12, numeral I49 represents the distance from the light source, 62, 63, to the area illuminated, and numeral I48 is the distance from the light source to the sev eral shielding means. The shielding means, at their greatest width, are so designed as to out 01f the M amount of light, as previously mentioned and this amount varies along the length of the cylinder as the distance I49 increases. It is to be understood that the spaces between the bars I2 changes during its bending and thus allowance must be made therefor.

Also, as more than one shielding means is used and thus the zones of light overlap it is sometimes necessary to utilize a slight correction factor. Also, the vanes are not continued to their ultimate points, as would theoretically be assumed, but compensation is made by the strips I3 and I4.

As is shown in Fig. these strips may be crimped in order to advance or retract the position of the screen upon the lamp in the direction of its axis, by reducing more or less the circumference of said strips I2. The screen is preferably perforated from a flat strip of metal, then bent about a mandrel to the required shape, the end connecting strips perhaps being crimped for the purpose of holding the vanes I2 away from the surface of the bulb.

Small bendable clips are provided for fastening the ends of the latticed shielding memher or screen together.

The length of the vanes is governed by the angle subtended between the points N and O and the light source as the shielding means should only be effective within that angle wherein light may be restricted.

In Fig. 6, the shaded areas P and I need extra light in order that the edges of the blueprints may be subjected to equal intensity of light and this is supplied by means of my reflectors. Arbitrarily dividing the area P into R, S, T and U it is found that R, by graphical measurement, needs 2 units of light, S needs 4 units, T needs '7 units and U needs 9 units. These units are merely the ratios needed with respect to one another.

As shown in Fig. 5, the hollow cone of light, designated 80, is free to be used as reflected light to eliminate the darker ends. It has been assumed that all of this available light is necessary. And, by proper manipulation of the light sources, and the like, this would be the condition. So, in Fig. 8, the light source may be considered either 52 or 63. I

The angle 'W-62V has been arbitrarily divided into 22 parts and since 9 of these must go to enhance the least lighted area U the reflector has been extended across 9 spaces, that is, from I00 to I Ill. And the angle has been made such that the angles I02 and I03 are equal. That is, the angle of incidence is equal to the angle of reflection.

It will also be understood that the 22 parts, into which the available light angle is divided, is the sum of the several units of light which are required.

Similarly, the next portion of the reflector extends across 7 spaces, from In! to I M, and is angularly positioned so that angles I05 and I06 are equal.

Next, the next section of the reflector is cut across to I61 and the last part of the reflector is to I08.

It will be understood that the reflector is gradually curved.

Thus it will be seen that all areas receive the same intensity of light for the purpose described.

My invention uses the principle of physics that a small opaque object, when positioned. near a source of light larger than itself, casts a shadow which diminishes to a point and thence disappears at progressive distances away from such object and light source, but at the same time diminishes the total sum or intensity of light reaching a point from such light source when such opaque object is interposed between such point and such light source in an amount equal to the size of the opaque object in its relation to the size of the light source and its relative distance from both. Specifically, determining the point upon the surface of the aforesaid cylinder receiving the minimum intensity of light due to its remoteness from light source, i. e. the lamp filament, and regarding this minimum as a desirable basic intensity to he maintained over the entire surface of the cylinder, the value of light reaching other points is calculated, some such points receiving more light than the aforesaid minimum due to their nearness to the lamp filament.

Subtracting the minimum amount of light regarded as basic from these more than the minimum intensities, and determining thereby the amount of surplus light reaching any point, opaque objects of calculated size and shape are interposed over the surface of the lamp bulb in such a manner that although no complete shadows shall be cast upon the working surface of the cylinder, the light reaching these hitherto overl-ighted points shall be'reduced in intensity in the approximate proportions of their hitherto undesirable surplus over the minimum regarded as basic.

As-is shown in Fig. 11, numeral IIU illustrates a lightbulb, looking at the end thereof, and the opaque shielding means III are painted or otherwise applied thereon. This is an approximate application of these means for shielding proportions of the light originating from the approximately circular filaments of certain bulb type lamps to the purpose of controlling light intensities upon a plane surface positioned perpendicularly to the axis of said lamp at a given distance from the light center thereof, and effective, of course,,on-ly over a given radius from the point where said axis intersects said plane surface.

Referring now to Fig. 7, a reflector I20 is shown. The rear surface is treated as at I2I so that the rays of light I22 and I24 are reflected as at I23 and I25, respectively.

Having thus revealed this invention, I claim as new and desire to secure the following combinations and elements, or equivalents thereof, by Letters Patent of the United States.

I claim:

In combination with a cylindrical surface to be uniformly illuminated, a pairof electric light bulbs located at the axis of said cylindrical surface and spaced from each other, each light bulb having a bulbous housing and a lighting filament within said housing, a light shield surrounding the girth of. each light bulb leaving its respective inner and outer ends unshielded, each light shield comprising a series of spaced segments and each 

